Single phase heat exchangers, such as “parallel flow” heat exchangers having multiple fluid conduits are described in U.S. Pat. No. 5,771,964. In such parallel flow heat exchangers, each tube is divided into a plurality of parallel flow paths of relatively small hydraulic diameter (e.g., 0.070 inch or less), which are often referred to as “microchannels”, to accommodate the flow of heat transfer fluid. Parallel flow heat exchangers may be of the “tube and fin” type in which flat tubes are laced through a plurality of heat transfer enhancing fins or of the “folded fin” type in which folded fins are coupled between the flat tubes. These types of heat exchangers have been used as cooling condensers in applications where space is at a premium. U.S. Pat. Nos. 6,347,662; 6,325,141; 5,865,243; and 5,689,881 further describe such heat exchangers having multiple conduits that serve as condensers.
The prior art associated with the cooling of computer chips and electronic components has utilized heat sinks of several basic types. Metal extrusions such as aluminum heat sinks have been used since the early days of computers when power densities were relatively low. These well known heat sinks have the disadvantage of low thermal performance (slow heat transfer), particularly when applied to systems operating at the high power density conditions of today's electronic devices and systems.
A second type of thermal management structure includes metal extrusions in combination with bases made formed from high thermal conductivity materials, such as copper or engineered materials or, even flat heat pipes. While addressing the heat spreading problem of metal extrusions, this type of heat sink still relies, in part, upon heat conduction through extended fins to external surfaces. Current extrusion techniques do not easily produce fins at the pitch and height required for high performance applications.
A third type of thermal management structure is a tower heat sink. Tower heat sinks often have a high conductivity core that is made of solid metal or heat pipes. Plate fins or machined structures surround the core to provide extended heat transfer surfaces. Heat is transferred upward through the core, then across the extended surfaces to be dissipated to the ambient environment. Assembly of plate fins to the core often requires manual labor which is expensive and sometimes yields inconsistent quality.
As a consequence, there continues to be a need for an improved heat sink for cooling electronic devices that satisfactorily meet today's high power density requirements while providing manufacturing flexibility.